In the bowl of a stand mixer fitted with a dough hook attachment, add all the dough ingredients. Knead for 20–25 minutes or until you can stretch a small piece of dough into a thin, translucent film (windowpane test). The dough should be well-hydrated, silky, and smooth but not sticky.

Wrap the dough in plastic wrap, forming a rectangle, and place it in the fridge for 30–40 minutes to relax. Prepare two baking sheets lined with parchment paper.

Meanwhile, prepare the filling. Whisk together the butter, sugar, and ground cinnamon until it reaches a soft, paste-like consistency.

Remove the dough from the fridge and place it on a lightly floured surface with the short side of the rectangle facing you. Roll it out into a 14 x 18-inch (35 x 45 cm) rectangle, about ⅕ inch (5 mm) thick.

Spread the filling evenly over the dough.

Grab the bottom third of the dough and fold it over the middle third. Then, fold the top third over the previous fold (this is called a letter fold).

Roll the dough slab to slightly widen it without making it longer.

Using a pizza cutter or a long knife, cut the dough into 15 strips, each about 1 inch (2.5 cm) wide.

Take one strip and gently stretch it to elongate it. Twist it 3–4 times to lengthen it further and seal the filling inside the dough. Coil the twisted strip into a spiral and tuck the loose end underneath. Place the bun on a prepared baking sheet and gently press to secure the tail so it doesn’t unravel during proofing and baking. Repeat with the remaining strips. When arranging the buns on the baking sheet, leave some space between them. I usually place a maximum of 8 buns per baking sheet.

Cover the trays with plastic wrap and let the buns proof for 1.5–2 hours or until puffy. Do not proof them in the oven with the light on, as the butter filling may melt and leak out.

Once the buns look puffy, brush them with the egg wash. Bake one tray at a time in a preheated oven at 425 F (220 C) for 10–12 minutes or until golden brown. It’s okay if some filling leaks out during baking, but if too much leaks, the strips were not twisted tightly enough.

Remove from the oven and allow them to cool before serving.